var dns = require('dns');
dns.reverse('202.165.102.205', function(e, domains){
	if(e)
		console.log(e);
	else
		console.log(domains);
});

/*
61.135.169.121 - 为dns.resolve('www.baidu.com' ... )的结果：
{ [Error: getHostByAddr ENOTFOUND]
  code: 'ENOTFOUND',
  errno: 'ENOTFOUND',
  syscall: 'getHostByAddr' }
*/

/*
202.165.102.205
[ 'unknown-202-165-102-x.yahoo.com' ]
*/